I love the simplicity of a good roadster. There is a purity to the direct connection between driver and vehicle, with no extra seats, no gadgetry, and so few distractions from the singular purpose of driving quickly. The lack of a roof means that you're in the environment, not just driving through it, enhancing the connection with the road. Lots of people like cars, but what roadster fans are really in love with is driving.

The 2013 BMW Z4 sDrive35is is not so simple. It's packed to the gills with tech. It's not quite at a Mercedes-Benz SL level of bloat and complexity, but it's also no spartan Mazda Miata. The dashboard is dominated by a large screen, gadgets, bells, and whistles. Overhead, there's the power-retractable hardtop that must weigh more than a ragtop. And while it makes up for the increased weight of the power roof and power leather seats with a turbocharged brute of an engine, it also sends its power through a computer-controlled dual-clutch automatic transmission and steers with electronic assistance that adds another layer of separation between the driver and the drive.

But there is such a thing as being too much of a purist and, despite these subjective critiques of the Z4, the sDrive35is model is still a pretty sweet ride and a proper roadster. The proportions are just right -- whether you love or hate BMW's visually complex style -- the performance is all there, the complexity that underlies that performance vanishes once you start chaining together corners, and the tech is fairly easy to master. More importantly, it simply begs to be driven with the top down.

Power-retractable hardtop
The Z4's power-retractable hardtop hides away and returns in about 20 seconds at the touch of a button. Sources say that the roadster needs to be stopped to activate the roof, but I was able to drop the top with the vehicle moving at parking-lot speeds.

The power hardtop retracts in about 20 seconds.
Josh Miller/CNET

The metal and glass of the roof and rear skylight intrude into the trunk when stowed, leaving only enough storage space for a pair of carry-on bags. With the roof raised, there is actually a reasonable amount of space that can be reclaimed, but because I consider driving a roadster with the roof up to be automotive blasphemy, let's just say that you won't be making a Costco run in this red toy, relegating it to second-car status.

A fabric roof would weigh less and take up less space, but there are, of course, advantages to a hard-roofed roadster: The vehicle is slightly more protected from thieves. The roof is less easily damaged. The cabin can be better insulated against rain, cold, and wind noise at the touch of a button.

The metal and glass of the roof intrude into the trunk, leaving very little space for stuff.
Josh Miller/CNET

You're also better insulated from the exhaust note, which can barely be heard with the hardtop in place. With the top down, you can enjoy the burble of the sDrive35is power train's exhaust, the whoosh of the induction, the wind around your ears.

With the top up, the Z4's curved roofline affords a bit of extra headroom for tall drivers, but even at 5' 9", I felt a bit claustrophobic after hours of open-air motoring. (You'll want to check out Brian's video for a taller driver's opinion.) From outside the car, the Z4's design also seems better-proportioned without the roofline's awkward hunch.

The power train
Beneath the Z4's endlessly long aluminum hood is the heart of the sDrive35is' power train: a 3.0-liter BMW TwinPower Turbo inline six-cylinder, which we've seen before spinning the wheels of BMW's 135is and 335is.

Output is stated at 335 horsepower and 332 pound-feet of torque thanks to the usual suspects of a twin-scroll turbocharger, variable valve control, and direct-injection technologies. The sDrive35is has a neat trick called Overboost that allows the turbocharged engine to temporarily increase its boost pressure under full throttle, bumping up the peak torque to 369 pound-feet for a short burst of acceleration. The driver doesn't need to do anything but plant the accelerator pedal to activate this feature.

The 3.0L turbocharged engine is a gem, delivering gobs of power.
Josh Miller/CNET

Speaking of pedals, the Z4 sDrive35is can only be had with two of them -- sorry, fans of clutch pedals -- as it is not available with a standard transmission option. The only gearbox available is BMW's seven-speed dual-clutch automatic transmission with paddle shifters. This transmission features sport and manual programs, the latter being controlled with either steering-wheel-mounted paddle shifters or the oddball BMW shift lever.

Power exiting the transmission heads to the rear wheels via a traditional open differential. No limited-slip diff, no torque-vectoring tech here. The Z4 is, however, capable of using its rear brakes as a sort of electronic differential to improve stability and traction.

Like many modern Bimmers, the Z4 uses a brake energy regeneration system to convert a bit of braking force into electrical power to charge the 12V battery, eliminating the need for an alternator and its parasitic drag and increasing fuel efficiency. The vehicle also makes use of electronic power steering to eliminate the need for a hydraulic power-steering pump to the same end.

The EPA estimates that the 2013 Z4 sDrive35is will average 19 mpg in this configuration. That's the combined average, which breaks down to 17 mpg in the city and 24 mpg on the hwy. I averaged about 20.4 mpg according to the Z4's trip computer, which was miraculous since I spent the week driving like an average BMW driver.

The performance
Z4 drivers have access to three Driving Experience modes with a rocker switch on the center console, but I didn't notice much difference between the Comfort, Sport, and Sport+ settings. The Driving Experience Control system adjusts the throttle response, the shift points of the gearbox, and -- when in Sport+ mode -- the characteristics of the DSC stability system. Were the Z4 equipped with the available adaptive suspension, the Driving Experience Control would also alter the roadster's dampers, but our tester was not so equipped, which probably explains why the Driving Experience modes felt so similar.

Fortunately, similar or not, the Z4's driving experience is a good one. With the deep burble of the sDrive35is' exhaust note urging me forward, the immediacy of the handling inspiring just a bit more daring, and the race car efficiency of the paddle-shifted gearbox, who could blame me for driving with a little extra zest? The Z4 is quick, but it also makes you feel awesome while sitting in the driver's seat.

The 335-horsepower Z4 is certainly not lacking in the power department. Thrust delivery is part linear, predictable, and intense -- particularly when you occasionally feel the extra surge of torque when the Overboost kicks in. Thanks to the standard DCT, the power delivery is also seamless, with almost no interruption for shifts.

The sDrive35is' drive train is only available with a seven-speed DCT automatic gearbox.
Josh Miller/CNET

Many are no doubt already typing comments lamenting the lack of a manual transmission -- I was initially disappointed as well -- but after a week with the DCT, I'm convinced that it is quite good. Wide-open throttle shifts happen faster than you can think about them, dropping into each gear with the immediacy of a shotgun kick and an audible snarl of the exhaust. Not only are those changes fast, but you can keep both hands on the wheel to tend to the business of actually cornering rather than shifting. Now, I love a good manual gearbox as well as the next guy -- heck, I love the bad ones, too -- but the dual-clutch is the future of performance driving, and I'm perfectly all right with that.

Gobs of power and bang-fast shifts are good, but the true measure of a roadster is how it handles a corner. Fortunately, the Z4 shines here, too.

The front-engine rear-drive configuration means that in most near-the-limit situations you'll be first met with a bit of understeer, which is good for safety. The Z4's seating position basically puts the driver over the rear wheels, for a near 50-50 weight distribution and reasonably neutral handling when you're within the roadster's generous performance envelope. Push the performance in the right way and oversteer is there when you need it, but it doesn't surprise you when you don't.

The low center of gravity, short wheelbase, and planted suspension make the Z4 surprisingly easy to drive. The ride feels planted when rounding a long, fast bend, but is also responsive enough to dart around hairpins, dodge potholes, and (with the DSC system off) give a bit of power oversteer when coaxed.

The electronic power steering is direct, predictable, and -- dare I say it? -- enjoyable, but it doesn't offer much in the way of fingertip feedback. The Z4's chassis makes up for this with good seat-of-the-pants feel, so it's not like you'll be flying blind.

It's got great power and good BMW handling, and it tops the driving experience with its top off. The Z4 sDrive35is is a grin generator, but I couldn't help but to think that it didn't feel that much better than the 135is that recently passed through the garage. The 1 Series coupe is a larger car, with a usable trunk and a back seat, meaning that it's actually useful for transporting people and things. The 1'er also has a slightly longer wheelbase that gives it an even more planted feel at highway speeds and around fast sweepers. Plus, it's nearly half the price.

We called the 135is the best car in BMW's current lineup: it's just as fast, more useful, and cheaper, so I couldn't help but feel that its very existence somewhat diminishes the value of the Z4. But then I realized that I'd been driving the Z4 sDrive35is with the top up, dropped it, and was all grins again.

The tech and options
Roadsters aren't typically known for their high-tech dashboards, but that doesn't stop BMW from offering its full suite of infotainment tech on the 2013 Z4.

Even without options, the standard technology loadout is pretty good. See again our review of the 135is for an idea of what to expect here. The short version: USB and iPod connectivity, analog audio input, CD playback, and AM/FM and HD Radio, all playing through a premium hi-fi audio system with surround sound. There's also standard keyless entry and start, one of my favorite features on new cars. It's not a bad setup, with a good array of audio sources and minimal distractions.

On top of that, our tester was equipped with the navigation system, which fills the ultrawide color display with the automaker's excellent 3D maps. Zoom in close enough and the map will be populated with 3D buildings; zoom out far enough and the map becomes topographic, displaying the elevation changes of the road ahead. You'll also get traffic data, satellite radio, and voice command for address entry, which is good in that it allows for the entire address to be spoken at once.

BMW's navigation system allows users to browse the Web for destinations with Google Local search.
Josh Miller/CNET

Also joining the tech party is Bluetooth for hands-free calling and address book sync for paired phones. Users can search for contacts using the iDrive control knob or the simpler voice command system. Bluetooth connectivity also includes audio streaming. Even after testing a half-dozen BMW vehicles, setting up my phone for Bluetooth audio streaming was confusing due to the weird way that the iDrive interface organizes its external audio sources, but after a day behind the wheel, navigating the system was second nature again.

Our vehicle was also equipped with BMW Apps, which allows certain smartphone apps to be accessed and controlled via iDrive. Available apps include Pandora, Glympse, Rhapsody, Audible, TuneIn, Stitcher, and BMW's own BMW Connected apps, but as of now only iPhone connectivity is supported.

One last tech oddity added with the navigation package is a center-console-mounted smartphone integration cradle. After purchasing an adapter for your iPhone or BlackBerry device, you can dock your phone in the center console where it will charge and sync with the iDrive system. As far as I can tell, the cradle doesn't do anything that the USB port and Bluetooth connection don't already handle, but even BMW's information on the functionality of this cradle is woefully inadequate.

The price tag and the Porsche
The 2013 BMW Z4 sDrive35is starts at $64,200, but our tester adds a few options. $550 coats the roadster in Melbourne Red Metallic paint. The 19-inch double-spoke alloy wheels add $1,200 and heated seats are $500. Then there are the navigation and apps packages that, together, add $2,400 to the bottom line. Factor in $895 for destination charges to reach our as-tested price of $69,745.

I've already mentioned that you could load up a BMW 135is for about half of that price and still have most of the fun, but the Z4 has a more premium cabin treatment and that power-retractable hardtop. The Z4 sDrive35is doesn't make a ton of financial sense, but at least it somewhat justifies its price.

The 2013 Z4 sDrive35is is a pretty sweet ride, but you'd have to be a die-hard BMW fan to chose this over the Porsche Boxster S.
Antuan Goodwin/CNET

However, the biggest argument against the Z4 comes from Porsche. The BMW Z4 sDrive35is with its DCT starts at $64,200, but a 2013 Porsche Boxster S starts at $62,100 with a standard manual transmission. Even with an additional $3,200 for PDK dual-clutch automatic gearbox, the two cars are quite closely matched.

Admittedly, while I have driven the 2013 Boxster, I've not driven the more powerful Boxster S, so I'm extrapolating a bit based on my overwhelmingly positive experiences with the non-S vehicle. The standard Boxster impressed me as one of the best roadsters I've ever driven -- its handling and driver involvement struck me as better than the top-tier Z4. The BMW is good, it goes where you point it, but the Porsche was sublime, it goes where you think it -- so it stands to reason that the Boxster S would be better still. Additionally, the Porsche's fabric roof doesn't intrude into its trunk as much and the mid-engine configuration means that you even have a second trunk on the front end. And while the BMW has much more power than the Boxster S, I believe that handling and the vehicle-driver connection carry more weight when you're talking about roadsters. If it's a drag race you're after, perhaps something with a Hemi would better suit you.

Admittedly, the Porsche closes the price gap and passes the Bimmer once you start laying on the tech and options, but if you're after a spartan roadster without all of the tech bells and whistles, I think I'd rather roll with the Porsche.